1. Field of the Invention
The present invention relates to a magnetoresistive element utilizing a magnetoresistive film such as a spin valve film, a tunnel-junction film, or the like. In particular, the invention relates to a current-perpendicular-to-the-plane (CCP) structure magnetoresistive element allowing a sensing current to have a component perpendicular to the surface of a substratum receiving a magnetoresistive film.
2. Description of the Prior Art
A magnetoresistive film is well known to extend rearward from the front end exposed at the medium-opposed surface or air bearing surface (ABS) by a predetermined length. The magnetoresistive film is interposed between a pair of domain controlling films made of a hard magnetic material. The domain controlling films serve to establish a biasing magnetic field across the magnetoresistive film in a predetermined direction. A single domain property can be realized in the predetermined direction in a free ferromagnetic layer in the magnetoresistive film based on the action of the biasing magnetic field.
The flow of the sensing current induces an annular magnetic field in the free ferromagnetic layer. The sensing current of a larger current value makes the annular magnetic field stronger. A stronger annular magnetic field tends to establish an annular magnetization within the free ferromagnetic layer. This hinders establishment of a single domain property in the free ferromagnetic layer. The influence of Barkhausen noise is supposed to appear in signals from the magnetoresistive film.
On the other hand, a stronger biasing magnetic field can be employed to reliably realize a single domain property in the free ferromagnetic layer even when the current level of the sensing current is set higher. The biasing magnetic field is opposed to some part of the annular magnetic field, so that the biasing magnetic field overcomes the annular magnetic field. However, the biasing magnetic field acts in the same direction as some part of the annular magnetic field. The magnetic field excessively acts in this direction in the free ferromagnetic layer. This hinder the rotation of magnetization in the free ferromagnetic layer. The sensitivity of the magnetoresistive film may be deteriorated.